RENAME TABLE allows InnoDB to replace mysql.general_log

MariaDB 12.3.3 allows an atomic RENAME TABLE to replace the CSV-backed mysql.general_log table with an InnoDB table. The rename succeeds and information_schema.TABLES reports InnoDB for the protected log-table identity.

This occurs when an atomic RENAME TABLE replaces a protected log table with a table using an ineligible storage engine.

Reproducer

Run the following as an administrative user. It disables general logging, performs the swap, records the installed engine, and immediately restores the original table and global setting.

CREATE DATABASE IF NOT EXISTS test;

SET @saved_general_log=@@GLOBAL.general_log;

SET GLOBAL general_log=OFF;

DROP TABLE IF EXISTS test.log_candidate;

DROP TABLE IF EXISTS test.log_moved;

CREATE TABLE test.log_candidate (a INT) ENGINE=InnoDB;

SELECT ENGINE AS original_engine

FROM information_schema.TABLES

WHERE TABLE_SCHEMA='mysql' AND TABLE_NAME='general_log';

RENAME TABLE

  mysql.general_log TO mysql.general_log_backup,

  test.log_candidate TO mysql.general_log;

SELECT ENGINE AS installed_engine

FROM information_schema.TABLES

WHERE TABLE_SCHEMA='mysql' AND TABLE_NAME='general_log';

RENAME TABLE

  mysql.general_log TO test.log_moved,

  mysql.general_log_backup TO mysql.general_log;

DROP TABLE test.log_moved;

SELECT ENGINE AS restored_engine

FROM information_schema.TABLES

WHERE TABLE_SCHEMA='mysql' AND TABLE_NAME='general_log';

SET GLOBAL general_log=@saved_general_log;

Observed result

The first rename succeeds and installs the InnoDB table as mysql.general_log:

original_engine

CSV

installed_engine

InnoDB

restored_engine

CSV

The inverse rename restores the original CSV table successfully.

Expected result

The first RENAME TABLE should fail and leave the CSV-backed mysql.general_log in place. MariaDB rejects InnoDB for this protected log-table identity through the engine-eligibility check used by CREATE and ALTER; changing the table's identity through RENAME should enforce the same invariant.